The aquatic phytotoxicity, or toxicity of waterborne contaminants on terrestrial and aquatic plants, is an important part of the environmental monitoring and land remediation programs. See for example “Handbook of Ecotoxicology”, Second Edition, D. Hoffman et al (Eds), page 191. The common practice for quantification of the effects of waterborne contaminants on vegetation is conducting laboratory experiments under controlled greenhouse or laboratory conditions. During these assessments, water and/or soil is retrieved from a location of interest and transported to the controlled environment where seeds and/or seedlings are exposed to the water/soil and parameters including seed germination and seedling growth are assessed. Typically, these experiments contain a control treatment with non-contaminated soils/water, or have been repeated over time to allow for a determination of baseline conditions in the area. Comparisons between the control and exposed treatments allow for the establishment of thresholds and are used as an assessment of contaminant effects. The data is then recorded and used as a reference for future assessments. Once such thresholds are established, the concentration of contaminants in soil/water samples can then be determined using analytical chemistry procedures and compared to established guidelines to ascertain if a contaminant effect should be expected. See for example, “Biological Test Method: Test for Measuring Emergence and Growth of Terrestrial Plants Exposed to Contaminants in Soil”, a 2005 publication by Environment Canada.
These approaches have a number of limitations that affect their usefulness in environmental monitoring and land remediation efforts. The above mentioned current approaches portray conditions present at one point in time (when the samples were collected) and cannot capture temporal variability in the abiotic factors that may influence plant growth. Common approaches are also bulky and require a significant amount of controlled laboratory space to host growing plants. They take a relatively long time to get conclusive results and therefore are not at all suitable for situations of environmental emergency. Current analytical techniques are not able to convey the bioavailability of a contaminant and therefore cannot accurately predict plant responses to exposure. Furthermore, the effects of contaminants on soil fungi, although crucial to plant ecosystem functioning, are not routinely included in contaminant analyses.
There has been, however, an effort at developing laboratory-based novel assays involving aquatic and plant fungi. For example, Twanabasu et al, Science of the Total Environment (2013, 447 pp. 450-457) provide an assay in which growth parameters of arbuscular mycorrhiza, soil dwelling fungi that form symbiotic associations with plants, correlates with the concentration of the contaminant, triclosan. However, this assay is designed for a laboratory-based, controlled environment and is not suitable for use in field assessments.
Seed germination used for education purposes can be carried out on a glass slide covered with a piece of filter paper for visualization of plant growth (see “Teaching Plant Anatomy” by R L Peterson, C A Peterson and L H Melville 2008). One or more of such glass slides is then placed into a standard coplin jar, partially filled with water. The water is wicked by the filter paper wetting the seed. This assay is used to visually observe the seed germination process in real time, and can be adapted to observe the effects of contaminants on the seed and fungal spore germination (see for example Stevens K J et al, 2009, Environmental Toxicology and Chemistry, 28 pp. 2598-2609). However, this assay is again developed to be used in a controlled laboratory environment, and cannot be deployed in the field without incurring a significant facility cost.
The company, Microbiotests, provides a seed germination test in which seeds are manually attached to a filter paper which is then attached to a plastic sheet and exposed to a water/soil sample to be tested. The length of roots after 3 days of exposure is used to judge the toxicity of the sample. While this test represents progress towards phytotoxicological monitoring, it cannot be used for real time monitoring of water/soil samples.
It would be advantageous to the field of environmental toxicology to provide a portable, field deployable, and economical system that could be used to access phytotoxicity under real field conditions.